Core B Abstract The role of the Trimer Production Core (Core B) is to support the work of the Research Projects by making appropriate quantities of high quality, soluble envelope glycoprotein trimers and related reagents. The Core will then provide the reagents to the Project Leaders and external collaborators, and to other scientists who request access to our team?s reagents. The Core will also share its knowhow and provide training, quality control and trouble-shooting services to the team. Dr. PJ Klasse will be Core Leader. Mr. Albert Cupo will direct the Core?s activities on a day-to-day basis. The tasks of the Core are outlined below. Other responsibilities related to the production of trimers and other relevant reagents may arise during the life of the award and will be accomplished as and when appropriate. Aim 1: To produce milligram quantities of high quality SOSIP trimers and related Env proteins in mammalian cell lines by transient transfection. The Core will produce, in appropriate quantities, any trimers that are designed and evaluated (in small-scale production runs) by Projects 1 and 2, and then selected for scale-up. The trimers will be assessed for purity and antigenic quality, then supplied to Projects 1 and 2, to external collaborators and to other colleagues who request our reagents. Aim 2: To create and use permanent cell lines expressing SOSIP trimers. The Core will use now established methods to make stable CHO, 293T or 293S cell lines expressing wild type or epitope-tagged SOSIP and germline-targeting trimers based on various genotypes, under non-GMP conditions. Aim 3: To guide and facilitate the production and purification of SOSIP trimers under GMP conditions, and to support clinical trials. A CMO (KBI Inc.) has successfully made multi-gram amounts of GMP-grade BG505 SOSIP.664 trimers under the direction of a consortium that also involves IAVI and the BMGF. A second translational program to produce GMP-grade GT1.1 trimers should be completed in Q2 of 2019. The Core has used its expertise to guide both programs and will continue to do so for any new ones, including by the creation and transfer of methods and the production of achievable quantities of reference standard trimers. The Core will also produce SOSIP trimers for use in clinical trial analytical programs. By providing a central service to both Research Projects, and external collaborators, the Trimer Production Core will be intimately involved in the scientific program of the entire HIVRAD team.